The present invention relates in general to imaging apparatus and, in particular, to monitoring the status of a consumable product, such as a printing medium cartridge, e.g., a toner cartridge for a laser printer or ink cartridge for an ink jet printer, and to identify the capacity of the consumable product.
Many image forming apparatus, such as laser printers, copy machines, and facsimile machines, utilize well known electrophotographic printing processes. These image forming apparatus use toner, or the xe2x80x9cinkxe2x80x9d of the imaging process, to print or copy the desired image or words onto a piece of paper or media.
A disposable toner cartridge is often used in imaging systems, such as laser printers, and is conventionally identified as a xe2x80x9cconsumablexe2x80x9d or xe2x80x9cconsumable productxe2x80x9d because of its limited xe2x80x9clifexe2x80x9d (i.e., the toner will eventually deplete or some other component will eventually wear out). The toner cartridge may include a toner reservoir, seal assembly, mounting member, development roller assembly, photoconductive drum assembly and charging corona or roller assembly. These items and other similar components are also commonly identified as consumables because they too have a limited life. The toner is contained in the toner reservoir, and is eventually depleted after a certain number of printing processes. Toner cartridges are available with different toner capacities, e.g., the toner may be depleted after printing approximately 2000 pages or 4000 pages.
Certain imaging systems (for example, certain laser printers) are designed to detect when the toner level nears depletion and are capable of displaying a status message such as xe2x80x9ctoner lowxe2x80x9d on a display panel. Low cost laser printers, however, cannot afford the expense of a continuous toner level sensor. Thus, printers use pixel counting to estimate the amount of toner remaining in a toner cartridge. However, the initial capacity of the toner cartridge must first be known if pixel counting is to provide a meaningful estimate of the remaining toner. Unfortunately, with the availability of different capacity toner cartridges, the initial capacity of a toner cartridge loaded into a printer is not necessarily recognized by the printer.
One possible solution to the problem posed by the unknown initial capacity of a toner cartridge is to require the user to identify the toner cartridge capacity during loading. However, if the user fails to identify or incorrectly identifies the capacity of the toner cartridge, the toner level pixel count is rendered inaccurate. Another solution is to use an electronic label in the toner cartridge that could inform the printer of the toner cartridge""s capacity. An electronic label, however, adds expense to the product.
Accordingly, there exists a need for a printer to inexpensively and reliably identify the capacity of a toner cartridge in order to correctly estimate the amount of toner remaining in the toner cartridge.
The capacity of a printing medium cartridge, such as a toner cartridge or an ink cartridge, can be identified using printed element counting, e.g., pixel counting or drop counting, and a single level printing medium sensor in accordance with the present invention. For example, when a new toner cartridge is loaded into a printing device, the printing device makes an assumption regarding the toner capacity of the toner cartridge. Pixel counting is used to estimate the remaining toner in the toner cartridge based on the assumed initial capacity of the cartridge. A toner sensor provides a signal indicating when the toner reaches a specified or known level of toner, e.g., 30 percent of the toner remains. The estimated remaining toner based on pixel counting is compared to the known level of toner to determine if the assumed initial capacity was correct. The comparison may occur when the toner sensor signal is provided or if the estimated remaining toner falls below the known level, e.g., 30 percent, and a toner sensor signal is not provided indicating that there is more than 30 percent of toner remaining in the toner cartridge. If the assumed initial capacity is correct, i.e., the estimated remaining toner approximately matches the known level of toner when the toner level signal is provided, the printer continues to estimate the remaining toner based on pixel counting.
If, however, the assumed initial capacity is incorrect, the difference between the estimated toner level and the known level is used to identify the actual toner capacity of the toner cartridge. A look-up table can then be used to recalibrate the pixel counting so that an accurate estimate of the remaining toner may be performed for the remainder of the toner cartridge life based on the actual toner capacity.
The present invention may be used, e.g., to determine the capacity of a toner cartridge used with electrophotographic printing devices or to determine the capacity of an ink cartridge used with ink jet printers.